A gabion is a structural unit consisting of a wire frame cage filled with rocks. Gabions are double twisted hexagonal woven galvanized steel wire mesh compartmented baskets with a rectangular box shape ) They are used to build structures such as river walling. This technique commonly uses a set of gabion 'blocks' or 'baskets' wired together. A rock 'mattress' is a relatively thin cage with comparatively large surface area, laid on the grade of the bank or bed. Gabion blocks and mattresses are often used in combination; the blocks provide the vertical gravity walling and the mattresses are placed below the blocks to provide scour protection. However, they may be installed separately, as block walls and mattress systems respectively Gabions are also widely used in weir and storm water drainage structures.

The first industrial manufacture of gabions began in 1894. Gabion units are known under several names. The systems most widely used in India.

Gabion blocks are typically 2-4m long, 2-4m wide and  0.5-1m thick. Gabion mattresses are typically 3-6m long,  1-2m wide and from 0.15-0.5m thick.